In a conventional process of manufacturing semiconductor wafers, a mechanical method such as grinding or polishing, or a chemical method using etching, is used to process the back surfaces of semiconductor wafers (hereinafter simply called “wafers”) to reduce the thickness thereof. When these methods are used to process the wafers, protective tape is applied to the front surfaces of the wafers in order to protect the front surfaces having wiring patterns formed thereon.
Thus, a wafer sent to a back-grinding process is suction-supported at the front surface (patterned surface) by a chuck table and the back surface is ground with a grinder. At this time, protective tape is applied to the front surface of the wafer since the pattern could be damaged under the stress of grinding occurring to the front surface or could be contaminated.
The wafer thinned by grinding of its back surface could easily be broken during the processing or transportation. The wafer, due to its deflection or bending, is difficult to handle. In order to avoid such inconveniences, a proposal has been made to apply two different types of protective tape to a wafer surface beforehand to prevent damage and bending of the wafer (see Japanese Unexamined Patent Publication 2000-331968).
Thus, a method has been proposed and implemented to separate in a separating step, all at a time, the two protective tapes applied to the surface of the wafer.
The use of protective tape in double plies as described in the above Japanese Unexamined Patent Publication 2000-331968 has an advantage in terms of wafer reinforcement, but has the following inconvenience encountered in the process of separating the protective tape.
When separating the protective tape in two plies all at once, a very strong separating force (pulling force) is applied at this time. Thus, the very strong pulling force applied at a time to the thinned wafer poses a problem of forcibly bending or damaging the wafer.